Method and apparatus for actuating an operating means for an automatic fire extinguishing apparatus

ABSTRACT

In a fire protection control system a thermally conductive filament strung in the protected area is connected to a fusible link which may include first and second conductive elements bonded together with a fusible bonding material. The link normally inhibits an actuating mechanism for a gas pressure operated fire extinguishing apparatus. The thermal conductivity of the filament is sufficient to conduct sufficient thermal energy from the protected area to the link to melt the fusible material when the thermal activity in the protected area rises above a predetermined level to trigger the actuating means for the fire extinguishing apparatus.

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United States Patent 11 1 1111 3,897,828 Glover Aug. 5, 1975 METHOD AND APPARATUS FOR ACTUATING AN OPERATING MEANS FOR Primary E.\'uminerM. Henson Wood, Jr. AN AUTOMATIC FIRE EXTINGUISHING Assistant E.\unzinerMichael Mar APPARATUS Attorney, Agent, or Firm-Crisman & Moore [76] Inventor: John A. Glover, 421 S. Dwight St.,

Dallas, Tex. 75211 [57] ABSTRACT In a fire protection control system a thermally conduc- [22] Flled' May 1974 tive filament strung in the protected area is connected [21] Appl. No.: 475,160 to a fusible link which may include first and second conductive elements bonded together with a fusible I bonding material. The link normally inhibits an actuat- [52] US. Cl. 169/43, 11669906706,- 1166951457, g mechanism for a g pressure Operated fire extim 51 I Cl A' 37/36 guishing apparatus. The thermal conductivity of the i i 42 33 filament is sufficient to conduct sufficient thermal en- 1 0 care ergy from the protected area to the link to melt the fusible material when the thermal activity in the prov tected area rises above a predetermined level to trig- [56] References (fled ger the actuating means for the fire extinguishing ap- UNITED STATES PATENTS paratlm 3,448,808 6/1969 Scofield et al. .1 169/42 X 3.773111 11/1973 Dunn 169/26 13 Clam, 13 Drawmg Flgures 9| 191 zj /j 7/ ll /A 28 1?2 2o a 2 s-|s| g 47 8| 2| l74 I75 S 23 3 A I03 I63 PATENTEU AUG 5 I975 SNEET PATENTEU AUG 5191s SHEET METHOD AND APPARATUS FOR ACTUATING AN OPERATING MEANS FOR AN AUTOMATIC FIRE EXTINGUISHING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automatic fire extinguishing apparatus and, more particularly, to a method of and apparatus for actuating an operating means for an automatic fire extinguishing apparatus.

2. Technical Considerations and Prior Art One of the three major causes of all hostile domestic fires is the accidental combustion of oil or grease on a residential kitchen cooking range. These are classified as Class B fires and comprise the majority of fires occurring in homes.

The most effective way of preventing range top fires from developing into general conflagrations is to employ automatic fire extinguishing apparatus. This is most effectively done by a fire extinguisher positioned above the cooking area of the range which is provided with a sensing means to sense the occurrence of a fire and extinguish and control it automatically.

One type of relatively inexpensive automatic fire extinguishing apparatus suitable for range top fires is disclosed in B. G. Dunn, US. Pat. No. 3,773,111. Dunn discloses an automatic fire extinguishing apparatus which includes a canister filled with a suitable fire extinguishing agent, for example, sodium bicarbonate, and formed with a plurality of apertures which are oriented to blanket the range top with the fire extinguishing agent when pressure is applied to the agent in the canister. The apertures are normally sealed with frangible seals which fracture when pressure is applied to the fire extinguishing agent by gas introduced into the canister from a propellant container mounted in the canister and actuated by flame or heat generated from or by the decomposition of a pyrotechnic cord strung around the area to be protected which is ignited by the fire. The pyrotechnic cord is of a type not spontaneously ignited by heat but by flame from a range top fire. Its main characteristic is that it burns rapidly when ignited by the flames of a range top fire. Such pyrotechnic cords may be formed into a braided wire from thin metallic filaments, for example, of paladium and aluminum. These cords are relatively expensive, difficult to manufacture and often difficult to obtain commercially. They present problems in that they must be handled with extreme care and stored in accordance with rigid safety regulations.

Other types of automatic fire extinguishing systems utilize fusible plugs or links which are in direct thermal contact with the heat generated by a fire in the area to be protected. While these systems are actuated by the heat of the fire rather than a flame they are relatively elaborate and thus are expensive to install and maintain. Additionally, since the heat normally generated above a kitchen range top is often relatively high such systems are susceptible to accidental actuation.

There is therefore a need for a relatively inexpensive automatic fire extinguishing apparatus for protecting range tops or the like from the danger of fire which apparatus may be actuated by heat and/or flame, has a quick response to excessive heat in the area to be protected and is able to withstand the heat normally generated in the area without accidental actuation.

SUMMARY OF THE INVENTION One object of the present invention is to provide a new and improved automatic fire extinguishing apparatus.

Another object of the present invention is to provide a new and improved method of and apparatus for actuating an automatic fire extinguishing apparatus.

A further object of the present invention is to provide a new and improved automatic fire extinguishing apparatus which has a quick response to the heat or flame generated by a fire in the area to be protected by the apparatus.

A further object of the present invention is to provide a new and improved automatic fire extinguishing apparatus which is provided with a safe, simple and reliable actuation mechanism whichmay be conveniently and safely manufactured and stored.

A further object of the present invention is to provide a new and improved automatic fire extinguishing apparatus which may be easily mounted on a kitchen range vent hood, a central air closet, a laboratory hood, a motor or engine compartment, or any other area requiring automatic fire control protection.

A further object of the present invention is to provide a new and improved actuating means for an automatic fire extinguishing apparatus wherein heat energy in the area to be protected is transferred to the actuating means for the fire extinguishing apparatus which may be thermally remote from the area to be, protected.

A method of triggering an actuating means for a fire extinguishing apparatus in a fire protection system for a defined area in accordance with the principles of the present invention, may include the steps of inhibiting the actuating means for the apparatus with a fusible inhibiting element, positioning a heat conductive filament in the area to be protected by the apparatus and placing the filament in thermal communication with the fusible inhibiting element whereby a sufficient portion of the heat energy in the protected area is transferred to the fusible element through the conductive filament to melt the fusible element when the temperature of the protected area rises above a predetermined value.

An apparatus for triggering an actuating means for a fire extinguishing apparatus in a fire protection system for a defined area, in accordance with the principles of the present invention, may include a fusible element for inhibiting the actuating means of the fire extinguishing apparatus and a heat conductive filament in thermal communication with the fusible element and positioned in the area protected by the apparatus, the filament being sufficiently thermally conductive to transfer a sufficient portion of the heat energy in the protected area to the fusible element to melt the fusible element when the temperature in the protected area rises above a predetermined value.

The actuating means may include a moveable element, for example, a pivotally mounted support, which carries a puncturing means, for example, a pin, and is moveable from a first position to a second position by a biasing means, such as a torsion spring. Means may be provided for supporting a puncturable container of pressurized fluid adjacent to the moveable element. The container may be punctured by the puncturing means on the support when the support is urged from its first position into its second position. A restraining means, for example, a resilient clip having a pair of projections aligned on opposite sides of the moveable element, releasably retains the element in its first position.

The fusible element may be in the form of a link which holds the projections on the resilient restraining clip in a closed position when the link is below its fusion temperature and releases the restraining means when it is above its fusion temperature. The link may be formed entirely of fusible material and may be formed from an alloy solder or a suitable thermoplastic material.

The preferred form of link includes two metallic elements, a base and a closure element, which are fusibly secured together.

BRIEF DESCRIPTION OF THE DRAWINGS A complete understanding of the present invention will be obtained from the following detailed description of a preferred embodiment thereof, when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a sectional view ofa fire extinguishing apparatus comprising an essential part of an automatic fire extinguishing system in accordance with the principles of the present invention;

FIG. 2 is a sectional view, taken along the lines 22 of FIG. 1, illustrating an actuating mechanism for the fire extinguishing apparatus of FIG. 1;

FIGS. 3-5 are enlarged, cutaway views of a portion of FIG. 2 disclosing more clearly the operative details of the actuating mechanism of FIG. 2 before and after the operation thereof;

FIG. 6 shows a resilient retaining clip, fusible link and a heat sensing filament which operate the actuating means of FIGS. 35;

FIGS. 7 and 8 are enlarged views of the fusible link, particularly illustrating its connection to the heat sensing and transfer filament;

FIG. 9 is a sectional view taken along the lines 99 of FIG. 1, illustrating the manner in which the fire extinguishing apparatus of FIG. 1 may be adjustably secured to a supporting bracket;

FIG. 10 is a front elevation, showing the manner in which the apparatus of FIG. 1 may be mounted on a vent hood above the cooking area of a kitchen range;

FIG. 11 is a bottom view of the vent hood of FIG. 10, showing the manner in which the apparatus of the invention is disposed to define a complete automatic fire extinguishing system;

FIG. 12 shows a typical intermediate hanger means for supporting the heat sensing and transfer filament in the area to be protected by the fire extinguishing system of the invention; and

FIG. 13 illustrates a terminal hanger means for the heat sensing and transfer filament of the system.

DETAILED DESCRIPTION Referring to FIG. 1 there is shown an automatically activated fire extinguishing apparatus 20, forming part of an automatic fire control system. The extinguisher 20 includes a canister 21, a free floating piston 22, an end cap 23 threaded onto the canister 21 and having mounted therein an actuator mechanism 26, a nozzle assembly 27 and a supporting bracket 28.

The canister 21, the piston 22, the end cap 23, the nozzle assembly 27 and the supporting bracket 28 and preferably molded from a high impact, high tensile strength, plastic resin, for example, polycarbonate.

First and second spaced plastic disks 31 and 32, each formed therethrough with central apertures 33 and 36, resepectively, and covered by frangible seals 37 and 38, respectively, define a sealed compartment 41 within the canister 21 for containing the piston 22 and defining a reservoir 42. The reservoir 42 is filled with a suitable dry pulverulent extinguishing agent 43, which may be, primarily for example, desiccated sodium bicarbonate, which is both nontoxic and noncorrosive.

The frangible seals 37 and 38 may be a laminated combination of thin metal foil, for example, aluminum, and paper coated with a thin film of copolymer material. The frangible seals 37 and 38 are preferably adhesively bonded to the disks 31 and 32, respectively, and should be sufficiently thin to rupture under relatively low pressure, for example, 8 to 10 psi.

The piston 22 includes a generally conical forward portion 46 extending from which is a cylindrical guide sleeve portion 47. The outer diameter of the sleeve 47 is slightly smaller, e.g., by approximately 0.004 to 0.012 inches. than the inner diameter of the compartment 41 of the canister 21.

The nozzle assembly 27 includes a circular plate 51 formed with a sleeve 52 having a plurality of internally formed projections 53 spaced circumferentially therearound which cooperate with a like plurality of locking lugs 56 formed on circumferentially spaced portions of a circular support plate 57 formed at the base of a hollow outlet chamber 58 formed on the canister 21. An O-ring 61 seated in a circular slot 62 formed in the support plate 57 provides a seal between the nozzle assembly 27 and the plate 57 when the nozzle assembly 27 is secured to the support plate 57 with the projections 53 on the plate 51 and the lugs 56 on the plate 57 are engaged to define a bayonet type locking arrangement between the nozzle assembly 27 and the canister 21.

The plate 51 is formed with four hollow arcuate projections 66 for supporting four swivel-mounted directional nozzles 67 thereon. Each nozzle 67 includes an outer sleeve 68 having an enlarged end portion 71 the internal radius of curvature of which is equal to the external radius of curvature of the supports 66, and an internal sleeve 73 formed with a flange 76 having an external arcuate surface having a radius of curvature equal to the internal radius of curvature of the arcuate projection 66. Each nozzle 67 is thus mounted for universal movement on the supports 66.

A seal between the end cap 23 and the canister 21 is provided by an O-ring 81 seated in a circular groove 82 formed in the end cap 23. A second pressurizable compartment 83 is thus defined between the end cap 23 and the disk 32. The compartment 83 houses the actuator mechanism 26 for the fire extinguishing apparatus 20.

As shown in FIG. 2, the actuator mechanism 26 includes a support plate 91 formed with a plurality of apertures 92 for receiving a plurality of projections 93 formed on the internal surface of the end cap 23. The plate 91 is secured on the projections 93 by lock nuts 95. A container of pressurized fluid or propellant cartridge 96, filled with a suitable gas under pressure, for example, carbon dioxide, and having a frangible disk 97 thereon which may be punctured to release the pressurized gas therefrom is supported on the plate 91. While various types of carbon dioxide cartridges are commercially available from various manufacturers, those built to military specifications such as MIL- C-5820 or MIL-C-601B are preferred, since the failure rate of commercially available cartridges does not provide sufficient reliability of operation for application in a fire extinguishing apparatus to meet the standards set forth for certification by organizations such as Underwriters Laboratories, Inc.

A reduced or neck portion 98 of the cartridge 96 (FIG. 3) is disposed in a U-shaped cradle 101 formed on the support plate 91 while the cylindrical body of the cartridge 96 is disposed between a guide wall 102 and a bracket support 103 (FIGS. 1 and 4). A bracket 105 is fastened to the bracket support 103 and is formed with a projection 106 which holds the cartridge 96 securely in place. A pin 107 extends from the support plate 91 through an aperture 108 formed in the bracket 105.

A lock washer 111, (FIG. 4) which may be disposed partially in a groove (not shown) circumferentially formed around the periphery of the pin 107, holds the bracket 105 thereon.

A puncturing mechanism for the cartridge 96 includes a tapered rigid pin 113 extending through a projection 114 on a U-shaped moveable element or support 115 pivotally mounted on the pin 107. The pin 113 also extends through a cylindrical stop 118 on the projection 114. The puncturing mechanism is held in a cocked or first position as shown in FIGS. 3 and 4 against the force exerted by a biasing means or torsion spring 121 (FIG. 4) disposed over the pin 107 by a spring clip 122. The spring 121 is torsionally stressed between a straight end 123 of the spring 121 which engages a lug 126 formed in' the mounting plate 91 and a curved end 127 of the spring 121 which engages the projection 114 on the U-shaped support 115.

As will be understood from the discussion below the spring clip 122 is releasable to permit the U-shaped support 115 to be driven in an are by the spring 121 from its first position to a second position to puncture the frangible disk 97 on the cartridge 96 as shown in FIG. 5 to release the pressurized fluid therein.

Referring to FIGS. 4 and 6, the spring clip 122 is formed from a wire which is bent at an intermediate section to form two projections 131 and 132 disposed in an aperture 133 formed in the bracket 105 and a blind aperture 136 formed in a boss 137 formed in the plate 91. The puncturing mechanism is inhibited by being retained in an enclosure 138 defined between a pair of arcuate sections 141 and 142 of the spring clip 122 and the projections 131 and 132 by a fusible element or link 143 disposed between the arcuate sections 141 and 142 and a pair of ends 146 and 147 of the spring clip 122 on opposite sides of the support 115.

Referring to FIGS. 7 and 8 the fusible link 143 includes a base portion 151 and a U-shaped closure element 152 bonded together by a suitable fusible material such as an alloy solder 153 which may be an alloyed composition of tin, lead and silver. The base 151 and the closure element 152 define an oval shaped aperture 154 which is disposed over the ends 146 and 147 of the spring clip 122 to hold the ends thereof together to retain the puncturing mechanism within the enclosure 138 of the spring clip 122 against the force of the spring 121. The base 151 may be formed from a suitable heat conductive metal or alloy, for example, steel, having first and second end straps 156 and 157 bent in a first direction away from the base 151 and a center strap 158 bent in the opposite direction to receive a heat conductive filament 161 therebetween. The base 151 is secured to the filament 161, for example by crimping the straps 156, 157 and 158 to place the fusible link 143 in thermal communication with the filament 161. The closure element 152 is preferably formed from the same metal as the base 151.

The filament 161, which may be a solid or a stranded wire, is preferably strung around an area to be protected by the fire extinguishing apparatus 20 and is formed from a highly thermally conductive material, for example copper or an alloy of copper and another suitable conductive metal such as aluminum.

The filament 161, is sufficiently heat conductive to transfer a sufficient amount of thermal energy from the area to be protected to the fusible link 143 to continuously monitor or sense the thermal activity in the protected area such that when the temperature in the area rises above a predetermined level the fusible material 153 which bonds the closure element 152 to the base 151 of the fusible link 143 will become sufficiently liquified to permit the spring clip 122 to be released, releasing the puncturing mechanism and allowing it to be propelled by the torsion spring 121 such that the pin 113 punctures the frangible disk 97 on the cartridge 96 as mentioned above and shown in FIG. 5.

As shown in FIG. 1, the conductive filament 161 extends from within the compartment 83 to the area to be protected through a countersunk aperture 162. A guide post 163 formed on the inside of the end cap 23 adjacent to the aperture 163 has disposed thereon a resilient sealing washer 166 which is held in place by a disk 167 which is force-fitted over the post 163 to hold the sealing washer 166 in place over a portion of the filament 161 to permit the compartment 83 to be pressurized by the gas released from the cartridge when the cartridge 96 is punctured to release the pressurized fluid therein. I

Upon actuation of the puncturing mechanism, the compartment 83 is pressurized very rapidly to a point wherein the frangible seal 38 is ruptured, permitting the gas to expand rapidly and force the free floating piston 22 away from the end cap 23 and toward the disk 31. Since outside diameter of the guide sleeve 47 on the piston 22 is somewhat smaller than the inside diameter of the canister 21, some of the expanding gas passes around piston 22 into the compartment 42 to loosen the extinguishing material therein and rupture the frangible seal 37. The piston 22 and the expanding gas passing thereby force the extinguishing agent 43 out of the compartment 41 through the aperture 33 in the disk 31, the chamber 58 and outwardly through the directional nozzles 67 to the area protected by the apparatus 20.

Referring to FIGS. 1 and 9 the bracket 28 for supporting the fire extinguisher 20 includes a plate 171 formed with first and second supporting members 172 and 173 depending transversely therefrom and formed with suitable grooves 174 and 175 to engage projections 176 and 177 formed circumferentially around the outside periphery of the canister 21. Each of the depending members 172 and 173 is formed with a pair of spaced projections 181 and 182 for receiving a pair of straps 183 and 184 which are connected to the opposite ends of a spring 186 disposed in a guideway 187 defined between the projections I76 and 177 around the underside of the periphery of the canister 21. The top of the plate 171 may be coated with an adhesive material 191 or formed with apertures (not shown) for receiving suitable fasteners to permit the support 28 to be fastened to the underside of a range hood or the like to support the fire extinguishing apparatus 20.

Referring to FIGS. 10 and 11 the fire extinguishing apparatus may be secured to the underside of a vent hood 192 located above the burners 193 of a kitchen range 196 adjacent to a filter housing 197 disposed beneath the hood 192. One to four wire hangers are secured to the corners of the filter housing 197 or to the hood 192. These hangers are shown in FIGS. 12 and 13. A plurality of intermediate hangers 198 are each formed with an aperture 201 therethrough for passing the heat sensing and transfer filament 161. A fourth hanger 202 (FIG. 13) is a terminal hanger which includes a plate or washer 203 which may be moveable toward and away from the bracket 202 by suitable means such as a screw 205 to secure the terminal end of the filament 161.

The nozzles 67 and the canister 21 may be adjusted such that each nozzle 67 is directed toward one of four burners 193 or one of four quadrants on the top of the range 196. Once the fire extinguishing apparatus is secured in place and the nozzles are suitably directed. a plastic solvent may be applied in the area between the supporting projections 66 and the nozzles 67 on the nozzle assembly 27, and between the hanger bracket 28 and the canister 21, such that the extinguishing apparatus is permanently bonded and directed and there is no danger that an accidental bumping or touching of either the canister 21 or the nozzles 67 will disturb the fixed positions thereof.

The nozzles 67 may have suitable coverings or plugs placed therein to prevent any grease vapors from building up deposits therein which may obstruct the nozzles.

In operation, should a grease fire or the like occur in a cooking utensil such as the skillet 206 of FIG. 10, the heat energy generated by the fire would be transferred to the filament 161 by convection or by the direct heat from the flame of the fire touching the filament 161. A sufficient amount of this heat energy is conducted along the filament to the fusible link 143 to melt the fusible material 153 and allow the ends 146 and 147 of the spring clip 122 to separate to permit the support 115 to be propelled by the torsion spring 121 to force the pin 113 through the disk 97 on the cartridge 96 to operate the fire extinguishing apparatus as described above, expelling the extinguishing agent 43 from the canister 21 out of all of the nozzles 67 to blanket the range top to extinguish and control the fire.

It has been determined experimentally that if sodium bicarbonate is used as the primary extinguishing agent a chemical reaction takes place when the sodium bicarbonate is heated to form sodium carbonate, water and carbon dioxide. A secondary reaction takes place wherein the sodium carbonate is heated to decompose to sodium dioxide and carbon dioxide. Thus an overlapping decomposition occurs wherein carbon dixode and water vapor are formed to extinguish the flame and cool the cooking utensil or vessel, the range top and the hood. A sufficient amount of calcium silicate may be added to the primary extinguishing agent to act as a desiccant and to absorb the flammable material to insure that reignition of the flammable material is inhibited, even though the burner beneath the utensil continues to burn, by raising the ignition temperature and saponification of the flammable material contained in the utensil. A suitable amount of calcium stearate is preferably added to the extinguishing agent to make it moisture and water resistant.

The fusible link 143 need not be made of conductive 5 metal but may be formed from suitable thermoplastic material which softens suitably at a desired temperature. for example, 150 to 250F to permit the spring clip 122 to release the puncturing mechanism as described. The conductive elements of the fusible link need not be fusibly bonded together but may be held with a strip or ring of suitable thermoplastic material.

The fusible material 153 may have any desired fusion temperature depending upon its composition.

Though the method and apparatus of the invention have been shown and described as being particularly suitable for fire protection systems for kitchen ranges, other applications thereof will be obvious to those having ordinary skill in the art which come within the spirit and scope of the invention.

What is claimed is:

1. A method of triggering an actuating means for a fire extinguishing apparatus in a fire protrection system for a defined area, which comprises the steps of:

inhibiting the actuating means for the apparatus with a fusible inhibiting element which is not in direct thermal contact with the area protected by the system;

positioning a thermally conductive filament in the area protected by the system; and

placing the filament in thermal communication with the fusible inhibiting element whereby a sufficient portion of the heat energy in the protected area is transferred to the fusible element through the conductive filament to melt the fusible element when the thermal activity in the protected area rises above a predetermined level.

2. The method of claim 1 including the step of thermally isolating said fusible inhibiting element from said protected area except through said filament.

3. An apparatus for triggering an actuating means for a fire extinguishing apparatus in a fire protection system for a defined area which comprises:

a fusible element for inhibiting the actuating means for the fire extinguishing apparatus, said fusible element not being in direct thermal contact with the area protected by the system; and

a thermally conductive filament in thermal communication with the fusible element and positioned in the area protected by the system, said filament being sufficiently thermally conductive to transfer a sufficient portion of the heat energy in the protected area to the fusible element to melt the fusible element when the temperature in the protected area rises above a predetermined value.

4. An apparatus as set forth in claim 3 wherein said fusible element is thermally isolated from the protected area except through saidfilament.

5. An apparatus for actuating a fire extinguishing apparatus in a fire protection system for a defined area which comprises:

a puncturing element movable between a first position and a second position;

means adjacent to said puncturing element for supporting a puncturable container of pressurized fluid in a predetermined position for puncturing by said puncturing element when said puncturing element is in said second position to release the pressurized fluid from the container;

biasing means urging said puncturing element into said second position;

restraining means for releasably retaining said puncturing element in said first position against the force of said biasing means;

a fusible element for holding said restraining means in retaining engagement with said puncturing element when said fusible element is below its fusion temperature; and

a thermally conductive filament in thermal communication with said fusible element and positioned in the area to be protected by the system, said filament being sufficiently thermally conductive to transfer a sufficient portion of the heat energy in the protected area to the fusible element to melt the fusible element when the temperature in the protected area rises above a predetermined value.

6. An apparatus as set forth in claim wherein said moveable element includes a pivotally mounted support, said puncturing means is a pin fixed to said support, said biasing means includes a spring urging said support into said second position, said restraining means includes a resilient clip having a pair of projections aligned on opposite sides of said support and closable toward one another around said support to releasably retain said support in said first position and said fusible element includes a link for holding said projections closed when said fusible element is below its fusion temperature.

7. An apparatus as set forth in claim 6 wherein said link is formed entirely from fusible material.

8. An apparatus as set forth in claim 7 wherein said link is formed from thermoplastic material.

9. An apparatus as set forth in claim 6 wherein said link includes a conductive base connected to said filament and a conductive closure element fusibly secured to said base.

10. An apparatus as set forth in claim 9 wherein said closure element is bonded to said base with an alloy solder having a predetermined fusion temperature.

11. An apparatus as set forth in claim 9 wherein said closure element is secured to said base with thermoplastic material.

12. An improved automatic fire extinguishing apparatus of the type including a sealed canister for receiving a pulverulent extinguishing agent, a free floating piston disposed in said canister, a pressure chamber disposed on the opposite side of said piston for receiving a puncturable container of pressurized fluid, an actuating mechanism for puncturing said container to pressurize said pressurechamber to drive said piston to expel said extinguishing agent from said canister. and a closable resilient restraining means for releasably inhibiting said actuating mechanism, said improvement comprising:

a fusible element for holding said restraining means closed at temperatures below the fusion temperature of said fusible element; and

a thermally conductive filament disposed in the area to be protected by the apparatus and in thermal communication with said fusible clement, said filament being sufficiently thermally conductive to transfer a sufficient amount of heat energy from said protected area to said fusible element to raise the temperature of said fusible element sufficiently close to its fusion temperature to trigger said actuating mechanism when the thermal activity in the protected area rises above a predetermined level.

13. The improvement according to claim 12 wherein said fusible element includes a conductive base formed with a pair of projections, a conductive closure element formed with a pair of projections and means for fusibly securing the ends of said projections on said base to the ends of said projections on said closure element to define an aperture for receiving said closable restraining 

1. A method of triggering an actuating means for a fire extinguishing apparatus in a fire protrection system for a defined area, which comprises the steps of: inhibiting the actuating means for the apparatus with a fusible inhibiting element which is not in direct thermal contact with the area protected by the system; positioning a thermally conductive filament in the area protected by the system; and placing the filament in thermal communication with the fusible inhibiting element whereby a sufficient portion of the heat energy in the protected area is transferred to the fusible element through the conductive filament to melt the fusible element when the thermal activity in the protected area rises above a predetermined level.
 2. The method of claim 1 including the step of thermally isolating said fusible inhibiting element from said protected area except through said filament.
 3. An apparatus for triggering an actuating means for a fire extinguishing apparatus in a fire protection system for a defined area which comprises: a fusible element for inhibiting the actuating means for the fire extinguishing apparatus, said fusible element not being in direct thermal contact with the area protected by the system; and a thermally conductive filament in thermal communication with the fusible element and positioned in the area protected by the system, said filament being sufficiently thermally conductive to transfer a sufficient portion of the heat energy in the protected area to the fusible element to melt the fusible element when the temperature in the protected area rises above a predetermined value.
 4. An apparatus as set forth in claim 3 wherein said fusible element is thermally isolated from the protected area except through said filament.
 5. An apparatus for actuating a fire extinguishing apparatus in a fire protection system for a defined area which comprises: a puncturing eleMent movable between a first position and a second position; means adjacent to said puncturing element for supporting a puncturable container of pressurized fluid in a predetermined position for puncturing by said puncturing element when said puncturing element is in said second position to release the pressurized fluid from the container; biasing means urging said puncturing element into said second position; restraining means for releasably retaining said puncturing element in said first position against the force of said biasing means; a fusible element for holding said restraining means in retaining engagement with said puncturing element when said fusible element is below its fusion temperature; and a thermally conductive filament in thermal communication with said fusible element and positioned in the area to be protected by the system, said filament being sufficiently thermally conductive to transfer a sufficient portion of the heat energy in the protected area to the fusible element to melt the fusible element when the temperature in the protected area rises above a predetermined value.
 6. An apparatus as set forth in claim 5 wherein said moveable element includes a pivotally mounted support, said puncturing means is a pin fixed to said support, said biasing means includes a spring urging said support into said second position, said restraining means includes a resilient clip having a pair of projections aligned on opposite sides of said support and closable toward one another around said support to releasably retain said support in said first position and said fusible element includes a link for holding said projections closed when said fusible element is below its fusion temperature.
 7. An apparatus as set forth in claim 6 wherein said link is formed entirely from fusible material.
 8. An apparatus as set forth in claim 7 wherein said link is formed from thermoplastic material.
 9. An apparatus as set forth in claim 6 wherein said link includes a conductive base connected to said filament and a conductive closure element fusibly secured to said base.
 10. An apparatus as set forth in claim 9 wherein said closure element is bonded to said base with an alloy solder having a predetermined fusion temperature.
 11. An apparatus as set forth in claim 9 wherein said closure element is secured to said base with thermoplastic material.
 12. An improved automatic fire extinguishing apparatus of the type including a sealed canister for receiving a pulverulent extinguishing agent, a free floating piston disposed in said canister, a pressure chamber disposed on the opposite side of said piston for receiving a puncturable container of pressurized fluid, an actuating mechanism for puncturing said container to pressurize said pressure chamber to drive said piston to expel said extinguishing agent from said canister, and a closable resilient restraining means for releasably inhibiting said actuating mechanism, said improvement comprising: a fusible element for holding said restraining means closed at temperatures below the fusion temperature of said fusible element; and a thermally conductive filament disposed in the area to be protected by the apparatus and in thermal communication with said fusible element, said filament being sufficiently thermally conductive to transfer a sufficient amount of heat energy from said protected area to said fusible element to raise the temperature of said fusible element sufficiently close to its fusion temperature to trigger said actuating mechanism when the thermal activity in the protected area rises above a predetermined level.
 13. The improvement according to claim 12 wherein said fusible element includes a conductive base formed with a pair of projections, a conductive closure element formed with a pair of projections and means for fusibly securing the ends of said projections on said base to the ends of said projections on said closure element to define an aperture for receiving said closAble restraining means. 